Combined esophageal MII and pH-monitoring allow for the timed correlation of esophageal pH changes with reflux events and achieve high sensitivity for the detection of acid (pH <4), weakly acidic (pH 4-7) and weakly alkaline (pH >7) reflux episodes. Use of this technology is bringing into focus the potential role of weakly acidic and weakly alkaline reflux in symptoms that persist despite acid suppressive therapy or anti-reflux surgery.